The detection and identification of trace components of gases and vapors in the atmosphere requires highly sensitive and specific techniques. Examples of such techniques are mass spectroscopy, ion mobility spectroscopy, and ion diffusion techniques. These techniques require that the trace components be ionized or form ion clusters in order to be detected. One apparatus for use in these circumstances is an ionization detection cell shown in U.S. Pat. No. 3,835,328.
It has been found that certain trace components are not easily ionized at atmospheric pressure, particularly in the presence of water vapor, and the sensitivity of the instrument for these substances is low. This can, to some extent, be corrected by a procedure which converts the recalcitrant components to forms, such as oxides, which are more easily ionized, and this can be done by judicious admixture of reactant gases such as ozone. This procedure has the disadvantage, however, that when concentrations of reactant gas are used sufficient to accomplish the desired results with particular trace components, the reactant gas has the effect of partially decomposing other trace components, so that the sensitivity of the apparatus to those other components is actually reduced.